Field of the Invention
The present invention relates to an imaging module and an endoscope.
Description of the Related Art
Conventionally, a small imaging module utilizing a solid-state image sensing device is known.
Such imaging module is used in, for example, an endoscope.
As the configuration of the imaging module, a configuration is known which uses a flexible substrate that is provided with a solid-state image sensing device in which a through-hole interconnection is formed (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2011-217887, and hereinbelow referred to as Patent Document 1).
In the imaging module disclosed in Patent Document 1, the flexible substrate is bent toward the opposite side of the imaging surface (toward the rear side of the solid-state image sensing device) from both sides of the portion of the flexible substrate on which the solid-state image sensing device is mounted so that the shape (projected shape) of the flexible substrate does not exceed the region defined by the outer shape of the solid-state image sensing device as seen from the imaging surface of the solid-state image sensing device.
Furthermore, as another configuration of an imaging module, a configuration in which a film is formed on a T-shaped multilayer ceramic substrate is known in which a solid-state image sensing device, an electronic component, a terminal connected to a signal cable, and wirings connected to a solid-state image sensing device are formed on the film (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2000-199863, and hereinbelow referred to as Patent Document 2).
In the step of manufacturing the imaging module using the flexible substrate disclosed in Patent Document 1, for example, there are problems in that the wirings formed on the flexible substrate are likely to be broken and it is difficult to stabilize the shape or the size of the wirings, and the reliability is low.
In the imaging module using the multilayer ceramic substrate which is disclosed in Patent Document 2, for example, the reliability thereof is high; however, it is necessary to provide a quite large number of layers in order to obtain the T-shaped multilayer structure.
Consequently, the multilayer ceramic substrate is not suitable to reduce the size of the imaging module, and there is a problem in that the cost of manufacturing the imaging module remarkably increases.
In other cases, the T-shaped multilayer structure can be manufactured by adhesively attaching a plurality of layers to each other; however, in this case, although the number of layers decreases, it is extremely difficult to maintain the accuracy of the positions at which the layers are adhesively attached to each other.
In the case of employing the above-described step of adhesively attaching the layers, adjacent layers are adhesively attached with an adhesive interposed therebetween. However, the adhesive exudes from between the layers which are attached to each other, and also it is difficult to stabilize the amount of adhesive exuding from between the layers.
As a result, it is not easy to manufacture the T-shaped multilayer structure by the above-described step of adhesively attaching the layers.